Nonnull annotations for native modules (#23353)

Summary:
This adds Nonnull annotations for interfaces and classes used for native modules for Android, to improve Kotlin developer experience, but also code quality checks.

[Android] [Changed] - Nonnull annotations for native module interfaces
Pull Request resolved: https://github.com/facebook/react-native/pull/23353

Differential Revision: D14018181

Pulled By: mdvacca

fbshipit-source-id: 09a583860a6075e1d6f6df8f479369ae96497133

ReactAndroid/src/main/java/com/facebook/react/bridge/NativeModule.java

@@ -9,6 +9,8 @@ package com.facebook.react.bridge;
 
 import com.facebook.proguard.annotations.DoNotStrip;
 
+import javax.annotation.Nonnull;
+
 
 /**
  * A native module whose API can be provided to JS catalyst instances.  {@link NativeModule}s whose
@@ -28,7 +30,7 @@ public interface NativeModule {
    * @return the name of this module. This will be the name used to {@code require()} this module
    * from javascript.
    */
-  String getName();
+  @Nonnull String getName();
 
   /**
    * This is called at the end of {@link CatalystApplicationFragment#createCatalystInstance()}